The Italian shot-stopper, who won the Yashin Trophy as the world’s best goalkeeper in 2021, was caught on the ball by the striker inside his own six-yard box.
PSG were a goal to the good after an hour of the second leg, and 2-0 up on aggregate as the clock ticked on Real’s hopes of reaching the quarter-finals.
But Donnarumma hesitated on the ball before a hopeful punt away from the onrushing Benzema, which only found Vinicius. The Brazilian’s cross back to his teammate was buried to give Los Blancos a sniff at a revival.
And Benzema punished the mistake with aplomb as he made it 2-1 to Real on the night, and all square on aggregate, after 76 minutes when he found space in the area to fire past Donnarumma again.
Within seconds of the kick-off, once again the Bernabeu erupted as Vinicius broke down the left and teed up Benzema to put Madrid ahead for the first time in the tie.
The hat-trick put the Frenchman on 30 goals for the season with a career total of 79 in the Champions League, a tally only bettered by Robert Lewandowski, Lionel Messi and Cristiano Ronaldo.